Heretofore, a pipe joint has been used for connecting fluid tubes to a fluid pressure device such as a cylinder. Such a pipe joint, for example as disclosed in Japanese Laid-Open Patent Publication No. 03-140697, is equipped with a cylindrical shaped coupling main body portion. In the interior of the coupling main body portion, a ring shaped sealing member is installed, and adjacent to the sealing member, latching pawls are provided, for engagement with a flow passage pipe, which is inserted into the interior of the coupling main body portion. In addition, when the flow passage pipe is inserted from one end side of the coupling main body portion, the sealing member, which has a rectangular shape in cross section, abuts against the outer peripheral surface of the flow passage pipe, so that leakage of the fluid via the outer peripheral surface of the flow passage pipe is prevented. Together therewith, the latching pawls bite into the outer peripheral surface of the flow passage pipe, thus preventing the flow passage pipe from being pulled out.
However, with the pipe joint of Japanese Laid-Open Patent Publication No. 03-140697, when a fluid is supplied from the other end side of the coupling main body portion and flows into the flow passage pipe that is connected to the other end side, the sealing member is pressed toward the latching pawls as a result of the fluid, and by pressing of the latching pawls, the depth at which the pawls bite into the flow passage pipe is made deeper. As a result thereof, when the supply of fluid is halted and the flow passage pipe is taken out from the coupling main body portion, cases are known to occur in which separation of the flow passage pipe is difficult due to the latching pawls biting excessively into the flow passage pipe.
Further, when the flow passage pipe is installed with respect to the coupling main body portion, the sealing member is pressed by the flow passage pipe, thereby deforming and displacing the sealing member. However, in this case, since there is no space into which the contact portion with the flow passage pipe can move, deformation of the contact portion is obstructed, and as a result, resistance occurs when the flow passage pipe is inserted.
Furthermore, in a situation where the flow passage pipe is installed with respect to the coupling main body portion, as a result of the sealing member being pressed upon and displaced by the fluid that flows through the interior of the coupling main body, the contact area of the sealing member with respect to the outer circumferential surface of the flow passage pipe is reduced, and there is a concern that the sealing characteristics of the sealing member may be deteriorated.